1847.] Geology of Lewis County. 273 



tlie early part of summer, or destroy it before ripe in autumn. 

 The corn crop is more liable than other grains to be injured by 

 these frosts. It is yet to be determined whether this condition will 

 be improved when the forests are cleared up and the land brought 

 under cultivation, or whether it is owing to some peculiar quality 

 of the soil which enables it to recieve less, or I'adiate more of so- 

 lar heat. A light sandy soil must be very liable to excessive ra- 

 diation of caloric by night, and will no doubt be found to be the 

 true cause of these Irosts which occur so frequently in such soils, 

 while neighboring districts exposed to equal conditions but of a 

 different quality of soil are exempt. 



There are several places in the town of Diana where the prim- 

 itive is overlaid by the Potsdam sandstone, as near Louisburg, 

 near Harrisville, and in the vicinity of Indian River Lake- 

 These cappings of sandstone are all of limited extent, and isolated 

 from each other, distinctly stratified, with the strata in one or two 

 places highly inclined, and so far as observed, entirely destitute 

 of fossils. 



An interesting locality of this rock, occurs in the town of Mar- 

 tinsburgh, resting upon the gneiss and passing under the lime- 

 stone. This occurs on Roaring brook, and near the East road: 

 the strata are nearly horizontal or conforming to the slightly un- 

 dulating sm-face of the subjacent rock, and do not in all exceed 

 six feet in thickness. 



It is made up of smoothly worn pebbles of quartz, and grains 

 of sand, consolidated in whole or in part by an oxide of iron, 

 which tinges it of a reddish color, and occasionally considerable 

 masses occur of a greenish color, or mottled with green and red. 



This is the first observed locality of the Potsdam sandstone west 

 of the great primary nucleus of northern New York, and adds a 

 new fact to confirm the law of uniform succession of rocky strata 

 as observed in the different members of the New York system. 



It also in a striking manner illustrates the thinning out of stra- 

 ta which often occurs; the formation occurring in great perfec- 

 tion in St. Lawrence and the other northern counties, while at 

 this place it is reduced to a thin and unimportant stratum, and 

 so altered in lithological character as to be scarcely recognized 

 except by its association as the same rock. 



Another fact of still deeper interest might here be alluded to, 

 namely, the entire absence of a member of the New^ \ork system 

 — the calciferous sandstone, which occurs so fully developed both 

 north and south of this locality. "Whether this intermediate dis- 

 trict occupied an insular position during the deposition of the cal- 

 ciferous sandstone, or whether it was deposited uniformly over 

 the entire surface, and afterwards swept away prior to the depo- 

 site of the succeeding rock, our present knowledge may not ena- 



